The proposed 3-year study will identify key product attributes, end-user preferences, and health service delivery determinants relevant to youth's adherence to sustained-release injectable pre-exposure prophylaxis (PrEP) for HIV, and to use these findings to inform product optimization and future research and programmatic activities. Youth constitute a key target population for injectable PrEP, and careful examination of these factors will inform the design of future efficacy and effectiveness trials and ensure development of a product that will achieve high uptake and use. HIV PrEP trials and demonstration projects have suffered from suboptimal adherence. Biomarker assessments of product use in several recent PrEP trials in sub-Saharan Africa indicate that youth experience the greatest challenges with adherence to daily PrEP. Our team has just commenced development of a thin-film polymer device (TFPD) for PrEP delivery; however, it is critical to examine end-user and health delivery system issues that may impact adherence in the early stages of product development and clinical testing. Although an injectable method will simplify product delivery and overcome many of the barriers to use of existing methods, uptake of and adherence to an injectable PrEP method by youth is not a foregone conclusion. Youth have distinct risk profiles and experience social and structural barriers that shape risk perception and adoption of HIV prevention practices. The proposed study will take place in Cape Town, South Africa, and will focus on men and women aged 18-24, who constitute one of the populations most at risk for HIV acquisition globally. The research will be led by an early-stage Investigator with extensive experience evaluating factors contributing to the acceptability and adherence to novel HIV prevention methods in this setting, in partnership with Investigators at the Desmond Tutu HIV Research Foundation in Cape Town, South Africa. In the first phase of the study, we will conduct qualitative in-depth interviews (IDI) with 60 young women and men who have completed injectable, vaginal ring, and oral PrEP studies, and are PrEP-experienced. Using a socio-ecological framework, we will explore end- user factors at the individual, intrapersonal, and structural levels that influence uptake of and adherence to new health technologies (Aim 1). This formative data will then inform the design of a computerized, questionnaire-based, discrete-choice experiment (or choice-format conjoint analysis) that will be administered to 600 PrEP-nave youth residing in a high-density township in Cape Town. We will determine the key product design and health delivery system attributes that are most preferable and salient to adherence for an injectable PrEP method for young people (Aim 2). Through dissemination meetings, research findings will be integrated into product development of our own team's TFPD development and clinical testing of existing and other novel sustained-release injectables.